The invention relates to a method of generating an image of a layer of an object, in which an examination zone is irradiated from a plurality of penetrating radiation source positions in order to generate separate single images, for each single image there being stored digital measurement values which are dependent on the absorption in its image points, for a layer image point of a layer in the examination zone there being derived, from the stored measurement values of the image points geometrically associated with the layer image point, an image value which corresponds to the absorption at the relevant point. The invention also relates to a device for performing this method.
A method of the kind set forth is known from German Patent Application p 32 37 572 corresponding to U.S. Pat. No. 4,630,296, and also from the magazine "Medical Physics", Vol. 12. No. 4, July/August 1985, pages 431 to 436. This method is suitable for forming X-ray layer images of so-called dilute objects, that is to say objects exhibiting a comparatively low X-ray absorption in most volume elements and a high absorption in few volume elements only. A preferred field of application is the imaging of arteries of the coronary vascular system which are filled with a contrast medium. For such objects, for example, the arteries of the coronary vascular system of a patient which are filled with a contrast medium, the known method produces substantially artefact-free layer images from only a few single images, in other words only a few radiation sources are required (for example, four).
For such examinations a spatial impression of the examination zone is often desirable. Such a spatial impression can be obtained, for example by simultaneously displaying two X-ray images formed from spatially neighbouring positions (stereo basis) so that each time one image is observed by one eye, or by consecutively displaying images formed from neighbouring positions so that the object as seen by the observer is "rotated". A combination of both methods is also possible.
This kind of spatial display, necessitates the availability of X-ray images formed from spatially neighbouring positions. This condition is not satisfied by the method described above, because it involves only the formation of a few images from perspectives which substantially deviate from one another, so that an observer cannot integrate two single images into a single stereo image.